Specific factors controlling proliferation and differentiation in normal and neoplastic rat anterior pituitary cells will be investigated. The role of folliculo-stellate cells which have putative paracrine functions in the anterior pituitary gland will be examined by isolating enriched populations of folliculo-stellate cells using flow cytometric cell sorting and discontinuous percoll density gradient centrifugation. These cells will be characterized by immunohistochemistry, electron microscopy, in situ hybridization and in situ polymerase chain reaction and used in co- culture studies with enriched populations of normal prolactin and growth hormone cells and with the neoplastic GH3 cell line. Folliculo-stellate cells are present in normal and hyperplastic pituitaries, but are absent in transplantable rat pituitary cell lines, so these analyses should provide new information about the regulatory role of these cells in the pituitary. The role of transforming growth factor beta (TGFbeta) in pituitary growth and differentiation will be investigated. Our preliminary studies indicate that estrogens down regulate and basic fibroblast growth factor (bFGF) up regulate TGFbeta1 mRNA in the normal pituitary gland in vitro and that TGFbeta1 inhibits cell proliferation in the GH3 cell line. In vitro and in vivo analyses with the GH3 cell line whose growth is stimulated by estrogen and with a pituitary cell line developed in our laboratory, the GHRH-CL1, whose growth is inhibited by estrogen will allow us to analyze the role of TGFbeta on pituitary cell growth and differentiation. We will use a cell line developed by targeted oncogenesis, alphaT3-1, as a model of gonadotroph tumors to learn more about cell proliferation and differentiation in gonadotroph cells and tumors. The chromogranin/secretogranin proteins and alpha subunit of glycoprotein hormones will be used as markers of differentiation in the analysis of nitric oxide synthase regulation in this cell line. The long term objectives of this study are to analyze the mechanisms by which hormones and growth factors influence proliferation and differentiation in pituitary tissues in order to learn more about the biology of normal and neoplastic pituitary cells. The data from these studies may lead to a better understanding of the development of pituitary neoplasms and may provide more effective means of treating these neoplasms.